Variable condenser



July 29, i924.

n.A s. MccRUM VARIABLE CONDEN'SBR Filed NGV. 24. 1923 2 Sheets-Sheet l l Je 2 a w 5 F 6 7 J 7. f// Lkvw 7 z .5.3. Me/ww July 29, 1924. lv1,502,869

D. S. MCRUM A VARIABLE: coNDENsnn l Filed Nov. 24. 1923 f 2 sheets-shut 2 mxxw /L Patented July 29., 1924.

UNITED vSTATES PATENT OFFICE.

VARIABLE CONDENSER.

Application tiled November 24, 1923, Serial No. 876,240.

To all whom it may concer/n:

Be it known that I, DOUGLAS S. MCCRUM,

` citizen of the United States, residing at Saranac Lake, inv the county of Franklin and State of New York, have invented certain new and useful Improvements in Variable Condensers, of which the following is a specification.

This invention relates to variable condansers capable of' general use, but particularly adaptedfor use in conjunction with radio apparatus.A

' he primary object of the invention is to generally simplify and improve variable condensers of this kind, whereby the same may meet with all of the requirements for `a successful commercial use.

-.\Another object of the invention is to so `construct a variable condenser as to reduce y"the usual electrical losses or leakage.

A further object of the invention is to provide a variable condenser that will be eX- tremely simple and durable in construction -as well as eicient `in operation, and Wherein readily and cheaply produced parts are utilized, which may be quickly assembled or taken apart for repair.

Other objects will become apparent as the nature of the invention is better understood,

so and `the same consists in the novel form, combination and arrangement of parts here inafter more fully described, shown in the accompanying drawings and claimed. I

In the drawings wherein like reference characters indicate corresponding parts throughout the several views,

Figure 1 is a top plan view of a variable .condenser constructed in accordance with the present invention.

Figure 2 is a longitudinal sectional View thereof, taken substantially upon the line 2-2 of Figure 1.

A, Figure 3 is'a transverse sectional view, taken substantially upon the line 3 3 `of Fi rel.

` igure 4 is a longitudinal sectiom taken substantially upon the line 4 4 of Fig- ,.ure 1. Figure 5 is an end elevational view of the V150 device shown invFigure 1. l j f Figure 6 is a rtransverse.'sectionalfview, ,Y taken substantially upon the line 6-6 of Figure2. l. kt

Figure 7 is a perspective view of one of the electrode cylinders, andv Figure 8 is an inner :tace view of one of the base plates of one of the electrodes.

The device consists essentially of two .electrodes 5 and 6 respectively, each of which is composed` of a plurality o1c concentriccyllndrical aluminum plates or cylinders 7 and 8 respectively, the cylinders of one electrode being arranged to move to a position vithin those ofthe other electrode without actual contact with the latter for varying the working capacity oi' the condenser.

As shown, the electrode 6 is made movable by mounting the same to slide on the rod 9 of hard rubber or other suitable insulating material, which rod has yits ends fastened centrally within opposed end plates 10 and 11, which are made of moldedy in sulating composition, such as balrelite.

The fixed electrode or` stator 5 is heldin place by ametal bushing 12 that passes through the central opening in the end lat'e 10, and in which the adjacent end o the rod 9 is'xed, this bushing 12 beingheld in place by means of' a nut 13 threaded upon the outer end thereof and against the outer face of the plate 10. The cylinders of each electrode are held in their proper concentric relation by means of a circular base or disc 13 having its inner face provided with cylindrical steps onto which said cylinders are telescoped and suitably secured, which base plate or disc 13 is of conducting material and the steps of which are generally indicated at 15. The disc 14 of the electrode 5 is suitably secured upon the inner end o the bushing;l l2,\while the disc 14 of the electrode 6 slidably moves along the rod 9.

Metal rods 16 further serve to space the end plates 10 and 11 and to brace andconnect the latter at the rear side of the condenser, the endpl'ates 10 and 11 being rovided with suitable openings through w ich the reduced ends of the rod 16 projects. By

reducing the ends of the rods 16 shoulders are' presented a ainst which the `plates 10 and ll'may be rawn by threading nuts 17 upon the reduced ends of the r0ds16 against the outer faces of the plates 10 and 11, as shown. .p Y

At the front of the condenser, a. slotted metal plate 18 is mounted, preferably by securing the ends of the plates 18 against the front edges of the end plates and 11 through the medium of screws 19 or the like, and whereby the plate extends parallel with the rod 9. A handle including a thumb knob and pointer 2O is provided for moving the electrode 6 along the rod 9, and this handle further includes a shank or rod 21 upon the outer end of which the knob and pointer 20 is fixed, and which extends inwardly thru the slot 22 of the plate 18. The shank 21 has a yoke 23 upon its inner end that partially embraces and is suitably centrally secured to the out-er cylinder ot' the electrode 6, whereby, when lateral movement is imparted to the handle, the electrode 6 4is caused to move along the rod 9. As shown in Figure 4, the slot 22 extends longitudinally of the plate 18 for a major portion of its length, and a resilient sheet metal contact strip 24 is fixed to one side of the shank 21 in position to have a sliding orvviping contact with one wall of the slot 22. This spring contact also holds the shank 21 lin contact with the opposite side wall of the slot 22, so as to frictionally retain the electrode 6 in any position to'which itis adjusted, and to prevent rotation of the electrode 6 about the rod 9. The electrical connection is made with the stator electrode 5, by means of a suitable wire 25 whose ends 4may be soldered or otherwise fastened to the base plate or disc 14 of said electrode 5, the Wire 25 extendingI through an opening in the plate 10 for this purpose. The electrical connection with the movable electrode 6 may be made through the medium 'of a suitable.

wire 26 that is soldered or otherwise fastened to the plate 18 adjacent the end plate 11, a`nd as theshankA 21 and yoke 23 are oi 6 and the wire 26. A .soft rubber yring or 4ment toward the electrode 5,

conducting material, the current' may pass between the other cylinder 8 of the electrode washer 27, which tted onto the outer end 0f the electrode 5 against the inner face of the plate 10, limits the travel of the electrede 6 and serves as a dust shield when the electrode 6 is adjusted to its limit of move- An vlar brackets 28 are suitably secured by bo ting or like, as at 29, against the outer sides of the 'forwardportions of the end plates 10 and 11, and provide means whereby the device may be clamped or otherwise secured to. a panel 30 or other similar-support. The lll 3.0 will be provided with a slot simi;-

to the. slot 22 in the plate 18, and through which the shank 21 ofv the handle extends whereby the indicator knob 20 will be po-I sitonedgontwardly ofthe panel fol` cooperatron with a suitabIe lmear scale (not show/n), which may be provided along one side of the panel'slot.

From the above description, it will.. be

i incasso seen that the working `capacity of the condenserI may be conveniently varied to a marked degree by sliding the electrode 6 .to a desired position With any vdesired portions of the cylinders of the movable electrode 6 disposed within similar portions ot the cylinders of the stator electrode 5 or vice versa in accordance with the usual general principle ofcondensers of this type.

The advantage of the present condenser consists in a reduction of the electrical losses or leakage as comparedto theusual rotarv types of condensers, which usual losses are mainly due to much greater length of rcug i edges on the plate than is presented by the present device, by reason 'of the cylindrical form of the plates thereof. rllie present device is also more nearly dust prooi, and particularly so due to the fact that when the condenser is in a position of maximum capacity, it is practically sealed against the entrance of dust through the use of the-washer 28. thus preventing accumulation of dust on the inner plate and the resultant loss of eiliciency through leakage. Obviously, condensers of this kind having diiierent maximum capacities may be constructed by changing the number or length of the concentric cylindrical plates employed or both.

From the above description, it is believed that the construction and operation as well as the advantages of the present construe tion* will be readily understood and appreciated by those skilled in the art.

What l claim as new is:

plates connected in spaced [relation by means of a rod to form a support,` a plurality of cylindrical -metallic members of diiienrent diameters all having their adjacent ends in electrical connection, said cylindrical members being -concentrically arranged one 1. A condenser comprising a pair of end within the other and forming one electrode,

upon the outer end of the first named elec-- trode for sealing relation with the adjacent end of the outermost cylindrical member of the second named electrode when said electrodes are adjustedltoward each other to maximum capacity position. y

2. A condenser comprising a pair of end plates connected inv spaced relation by means ofl a. rod to form a` support, a plurality of c lindrical metallic members ot dierent diameters all having their adjacent ends in .electrica-l connection, said cylindrical meinvtrieally connected to form a bers being `concentrieally arranged one within the other and formingv one electrode,

means for mounting said one electrode inl fixed relation to one of the end plates and said rod, a series of similar cylindrical-members coneen'triealiy arranged 'one Within the other, and all having their; outer ends eleotlie members of said second electrode adapt- 1 edto be inserted between the members of VVeonrlueting\material attachedto the outer eylindrical' metallic eylinderlof one of the electrodes andhaving resilient Contact secured to one side thereof position vto' have' wiping contact with one side wallxof the slot of said slotted` A eondensereomprising a .pair offend nietes eonneeted in spaced relation byrneans of a rod to form a 4members of different diameters all having their adjacent ends in second electrode,x o

.of the first named support, a plurality of'` bers being concentrically f arranged one within the other and forming one electrode, means for mounting said one electrode -in fixed relation to 'one of the end plates' and said rod, a series of similar cylindrical memhers conce'ntrially arranged one Within the electrical connection. said cylindrical mem- -other and all having their-outer ends electrically connected to 'form va second elec'- trode, the' memberso said second electrode adapted to be inserted-between the members electrode', means ineluding ailiandle fixed to and extending laterally from the -'outermost cylindrical member of the electrode for adjusting'the latter axially of each other, a plate provided with 'a longii and rigidly connect# tudinal elongated slot ingtlie forward edges of said end'platefsad slotted plate being of conducting material, said'handle including a shank of conducting material attached to the outer cylinder of one of theelectrodes and 'Contact secured to oneside thereof in' position to have wiping .Contact with one side slotted plate, brackets Wall of. the slot of said fixed to the forward edge portions of said end plate for rigidly mounting the support parallel with and adjacent the rear face of a. panel, and means to connect the stepped disc of one electrode and the slotted plate to 'Wires of an electrical circuit.

In testimonywhereo l afiix DOUGLAS S.

mv signature y Messner.

having a resilient 

